The investing world has gotten less perilous since Gilded Age speculator Daniel Drew uttered these words. But the fight over Herbalife Ltd. has taken on a more personal, distinctly 19th century flavor. Rather than a battle among faceless institutions, as is usually the case today, Herbalife features a handful of financiers—Bill Ackman, Carl Icahn and George Soros—in a high-stakes duel.